1. Field of the Invention
This invention relates generally to valves, and more specifically to an improved integral fluid flow valve stem.
2. Description of the Prior Art
It is known in the prior art to provide a fluid flow valve stem comprising a sleeve having an internally threaded mouth by means of which a valve core may be retained in sealing engagement with a valve seat formed inwardly of the mouth. A disadvantage of such a fluid valve, of which U.S. Pat. No. 3,712,326 is exemplary, is that the valve core is a separate unit of complicated design and construction which is screwed into the valve stem. The valve core has a first seal member for engaging the valve seat of the stem to provide a permanent seal therebetween. In addition, the valve core has a valve seat of its own and a second seal member movable by a plunger relative to its valve seat between open and closed positions.
It is also known in the prior art as exemplified by U.S. Pat. No. 2,822,817 to provide a filler valve having a sleeve to which a reciprocally movable valve seal member is permanently secured. A disadvantage of this filler valve is its increased cost of manufacture due to the necessity of costly machining operations and the requirement of one or more sub-assembly operations. In addition, a costly final assembly operation of the filler valve is required in which a hollow stop member is inserted in the sleeve, depressed against a spring to a position past an internal retaining groove in the sleeve, and a retaining ring mounted in the groove.